/*************************************************************************
  > File Name: 06.cover_letter.c
  > Author: icebear
  > Mail: 3322366195@qq.com
  > Created Time: Fri 14 Jul 2023 03:04:20 PM UTC
请输入一个字符，实现大小写转化
 ************************************************************************/

#include <stdio.h>
int main()
{
    while(1)
    {
        char c = 0;
        printf("\ninput just one letter\n");
        c = getchar();
        getchar();
        if('a'<=c&&c<='z')
        {
            c-=32;
            printf("capital letter is  %c\n",c);
        }  
        else if('A'<=c&&c<='Z')
        {
            c+=32;
            printf("lower letter is  %c\n",c);
        }
        else
        {
            printf("error input\n");
        }
    }
}

